The aims of the funded RO1 grant "K-Channels in Lymphocyte Function and Autoimmunity" is to correlate numbers of myelin-specific Kv1.3high activated effector memory (TEM) T cells with disease activity in multiple sclerosis (MS) patients, pre and post treatment. 2. Evaluate the therapeutic effectiveness of Kv1.3 and KCa3.1 blockers in chronic relapsing-remitting experimental autoimmune encephalomyelitis (CR-EAE) in rats. 3. Determine whether disease-associated insulin- and GAD65-specific T cells in type-1 diabetes mellitus (T1DM) patients exhibit the Kv1.3high activated-TEM pattern. Ms. Adriana Garcia, the candidate, has participated in two related projects during the 1 year in the lab. (Project 1) She showed that ShK-186, a specific blocker of Kv1.3 channels, treated CR-EAE in DA rats, and at therapeutic concentrations did not compromise the immune response to chlamydia trachomatis. These data have been submitted for publication. (Project 2) She generated preliminary data to demonstrate the feasibility of a non-invasive method to image pancreatic beta cell loss during T1DM. Such a method would enable early recognition of therapeutic efficacy of Kv1.3 inhibitors. The present proposal is an extension of project-2. Adriana will test the hypothesis that PET-CT scanning with 18F-fallypride, a radioligand for D2 receptors (D2R) for dopamine, can document [unreadable]-cell loss associated with T1DM. D2R are present in rodent and human islets, where they co-localize intracellularly with insulin-containing secretory granules in [unreadable]-cells. In preliminary studies Adriana used autoradiography and micro PET ex vivo imaging to show specific 18F-fallypride binding to pancreatic islets and not the exocrine tissues. Based on her data, a collaborator did a 18F-fallypride PET/CT study in a human volunteer and was able to detect 18F-fallypride binding to the human pancreas. We have been awarded a JDRF Pilot Grant to determine if 18F-Fallypride PET-CT imaging of the pancreas can detect an "all or none response" by comparing 12 patients with longstanding T1DM and 12 healthy controls. The goals of Adriana's proposal complement the human studies by correlating micro PET 18Ffallypride data with histopathology, and by determining the sensitivity of PET for detecting fc-cell loss. Aim-1: Determine time-dependent distribution of specific 18F-fallypride binding in different tissues in rats using microPET/CT. Aim-2: Measure [unreadable]-cell mass in normal and streptozotocin-treated diabetic rats using microPET/CT. Aim-3: Measure [unreadable]-cell mass in pancreas during the spontaneous age-dependent development of DM in BB rats and in BB rats treated with the Kv1.3 blocker PAP-1.